Numerous empirically supported preventive evidence-based practices (EBPs) have been developed that show improved outcomes on avoidance of drug use and HIV risk for vulnerable children, yet few are actually assimilated into child welfare systems (CWS) to the point where they have a measurable public health impact. Related, measures ofthe processes of installing EBPs in agencies and systems are needed to close knowledge gaps on factors that contribute to successful/failed implementation. This project capitalizes on previous work on the development of a measure of implementation success/failure (the Stages of Implementation Completion) and on a unique opportunity to study the roll-out of the implementation of two NlDA-funded preventive EBPs within the CWS in New York City. The Administration for Children's Services (ACS) is currently reforming the City's CWS to use Keeping Foster Parents Supported and Trained (KEEP) and Parent Management Training (PMT) to strengthen caseworker and supervisor skills to work with CWS parents, and to increase the potential for achieving key system level outcomes. Both KEEP and PMT are OSLC-developed evidence-based preventive interventions that have been rigorously evaluated in a series of NlDA-funded efficacy and effectiveness trials. In this scale-up study in 33 child welfare agencies, we will examine; a) the relationship of intervention fidelity in KEEP and PMT to child and family outcomes measured by using existing administrative data, b) the utility of providing agencies with information on the costs per stage of implementation, and c) using mixed methods, the factors which predict sustainability versus dead option of KEEP and PMT interventions. Together, these Aims will increase our understanding of what factors help to increase the potential for successful implementation and scale-up of linked evidence-based preventive interventions within the child welfare system.